Systems and methods for enhancing dynamic response of power conversion systems

ABSTRACT

System and method for regulating a power conversion system. For example, a system controller for regulating a power conversion system includes an amplifier, a variable-resistance component, a capacitor, and a modulation and drive component. The amplifier is configured to receive a reference signal and a feedback signal associated with an output signal of the power conversion system, the amplifier including an amplifier terminal. The variable-resistance component is associated with a first variable resistance value, the variable-resistance component including a first component terminal and a second component terminal, the first component terminal being coupled with the amplifier terminal. The capacitor includes a first capacitor terminal and a second capacitor terminal, the first capacitor terminal being coupled with the second component terminal. The modulation and drive component includes a first terminal and a second terminal, the first terminal being coupled with the amplifier terminal.

1. CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to Chinese Patent Application No.201210236882.2, filed Jul. 9, 2012, commonly assigned, incorporated byreference herein for all purposes.

2. BACKGROUND OF THE INVENTION

The present invention is directed to integrated circuits. Moreparticularly, the invention provides systems and methods for enhancingdynamic responses. Merely by way of example, the invention has beenapplied to power conversion systems. But it would be recognized that theinvention has a much broader range of applicability.

A switching power conversion system often needs not only a good dynamicresponse under different load conditions, but also good stability. FIG.1 is a simplified diagram showing a conventional switching powerconversion system with a step-down structure. The switching powerconversion system 100 includes a system controller 102, a switch 104, acapacitor 106, two diodes 108 and 110, and an inductor 112. For example,an output voltage 120 of the power conversion system 100 usually needsto be regulated to be approximately constant, and relatively stable ifoutput load varies.

FIG. 2 is a simplified conventional diagram showing certain componentsof the system controller 102 as part of the power conversion system 100.The system controller 102 includes an error amplifier 202, a controlcomponent 204, and a gate driver 206. In addition, the system controller102 uses a compensation network 208 that includes capacitors 210 and 212and a resistor 214.

The error amplifier 202 receives a feedback signal 216 that is relatedto the output voltage 120 and a reference signal 218 and generates anamplified signal 220 which indicates load conditions of the system 100.The control component 204 receives the amplified signal 220 and outputsa modulation signal 222 to the gate driver 206 which generates a gatedrive signal 224 to drive the switch 104. The compensation network 208is connected to an output terminal of the error amplifier 202. If theamplified signal 220 is large in magnitude which indicates that theaverage output voltage 120 is far different from the reference signal218, the control component 204 adjusts the modulation signal 222 toincrease the switching frequency and duty cycles so that more power canbe delivered to the output load.

A bandwidth of the control loop often needs to be very small in order toregulate the output voltage 120 to be approximately constant. Thedominant pole of the control loop is associated with the error amplifier202 and the compensation network 208. Usually, the capacitor 212 has alarge capacitance in order to reduce the bandwidth of the control loop.But, the large capacitance of the capacitor 212 negatively affects thedynamic response of the power conversion system 100 if the loadconditions change.

To achieve a good dynamic response, a wide bandwidth of the control loopfor the power conversion system 100 is often needed. For example, thecompensation network 208 can be removed to increase the bandwidth of thecontrol loop. Then, the error amplifier 202 becomes a comparator, andthe output of the error amplifier 202 changes from rail to rail whichresults in significant changes in switching frequency and duty cycles.The power conversion system 100 thus operates in an on-off mode (e.g.,an ON/OFF mode), instead of an error amplifier mode (EA mode). The widebandwidth of the control loop, however, often negatively affects thestability of the power conversion system 100, even if the output load issteady. A complex compensation network with a large number of externalcomponents is usually needed to obtain both good dynamic response andsatisfactory stability. But such a compensation network oftensignificantly increases the system cost.

Hence it is highly desirable to improve the techniques of enhancingdynamic responses of power conversion systems.

3. BRIEF SUMMARY OF THE INVENTION

The present invention is directed to integrated circuits. Moreparticularly, the invention provides systems and methods for enhancingdynamic responses. Merely by way of example, the invention has beenapplied to power conversion systems. But it would be recognized that theinvention has a much broader range of applicability.

According to one embodiment, a system controller for regulating a powerconversion system includes a first amplifier, a variable-resistancecomponent, a first capacitor, and a modulation and drive component. Thefirst amplifier is configured to receive a reference signal and afeedback signal associated with an output signal of the power conversionsystem, the first amplifier including an amplifier terminal. Thevariable-resistance component is associated with a first variableresistance value, the variable-resistance component including a firstcomponent terminal and a second component terminal, the first componentterminal being coupled with the amplifier terminal. The first capacitorincludes a first capacitor terminal and a second capacitor terminal, thefirst capacitor terminal being coupled with the second componentterminal. The modulation and drive component includes a first terminaland a second terminal, the first terminal being coupled with theamplifier terminal, the modulation and drive component being configuredto output a drive signal at the second terminal to a switch in order toaffect the output signal of the power conversion system. The systemcontroller is configured to set the first variable resistance value to afirst resistance magnitude in order to operate in an on-off mode, andset the first variable resistance value to a second resistance magnitudein order to operate in an error amplifier mode. The first resistancemagnitude is larger than the second resistance magnitude. The on-offmode is different from the error amplifier mode.

According to another embodiment, a system controller for regulating apower conversion system includes a first amplifier, a second amplifier,a first capacitor, a first switch, a second switch, a third switch, afourth switch, a first resistor, and a second resistor. The firstamplifier includes a first input terminal and a second input terminaland a first output terminal. The second amplifier includes a third inputterminal and a fourth input terminal and a second output terminal. Thefirst capacitor includes a first capacitor terminal and a secondcapacitor terminal. The first switch includes a first switch terminaland a second switch terminal. The second switch includes a third switchterminal and a fourth switch terminal. The third switch includes a fifthswitch terminal and a sixth switch terminal. The fourth switch includesa seventh switch terminal and an eighth switch terminal. The firstresistor includes a first resistor terminal and a second resistorterminal. The second resistor includes a third resistor terminal and afourth resistor terminal, the second resistor being associated with avariable resistance value. The seventh switch terminal is coupled to thesecond output terminal. The eighth switch terminal is coupled to thefourth input terminal, the first capacitor terminal, the second switchterminal, and the first capacitor terminal. The third switch terminal iscoupled to the fifth switch terminal. The fourth switch terminal iscoupled to the third resistor terminal. The fourth resistor terminal iscoupled to the sixth switch terminal, the first resistor terminal, andthe first switch terminal.

According to yet another embodiment, a system controller for regulatinga power conversion system includes a variable-resistance component, afirst amplifier, a first capacitor and a modulation and drive component.The variable-resistance component includes a first component terminaland a second component terminal and is associated with a first variableresistance value. The first amplifier is configured to receive areference signal and a feedback signal associated with an output signalof the power conversion system, the first amplifier including anamplifier terminal coupled with the first component terminal, the firstamplifier being further configured to generate, with at least thevariable-resistance component, a first signal based on at leastinformation associated with the feedback signal and the referencesignal. The first capacitor includes a first capacitor terminal and asecond capacitor terminal, the first capacitor terminal being coupledwith the second component terminal. The modulation and drive componentincludes a first terminal and a second terminal, the first terminalbeing coupled with the amplifier terminal, the modulation and drivecomponent being configured to output a drive signal at the secondterminal to a switch in order to affect the output signal of the powerconversion system. The system controller is configured to set the firstvariable resistance value to a first resistance magnitude in order tooperate in a first mode, and set the first variable resistance value toa second resistance magnitude in order to operate in a second mode. Thesystem controller is further configured to, in the first mode, if thefeedback signal changes from a first signal magnitude to a second signalmagnitude, change the first signal from a third signal magnitude to afourth signal magnitude during a first time period. The systemcontroller is further configured to, in the second mode, if the feedbacksignal changes from the first signal magnitude to the second signalmagnitude, change the first signal from the third signal magnitude tothe fourth signal magnitude during a second time period, the second timeperiod being longer than the first time period in duration.

According to yet another embodiment, a system controller for regulatinga power conversion system includes a variable-resistance component, afirst amplifier, a first capacitor and a modulation and drive component.The variable-resistance component includes a first component terminaland a second component terminal and is associated with a first variableresistance value. The first amplifier is configured to receive areference signal and a feedback signal associated with an output load ofthe power conversion system, the first amplifier including an amplifierterminal coupled with the first component terminal, the first amplifierbeing further configured to generate, with at least thevariable-resistance component, a first signal based on at leastinformation associated with the feedback signal and the referencesignal. The first capacitor includes a first capacitor terminal and asecond capacitor terminal, the first capacitor terminal being coupledwith the second component terminal. In addition, the modulation anddrive component includes a third component terminal and a fourthcomponent terminal, the fourth component terminal being coupled with theamplifier terminal, the modulation and drive component being configuredto output a drive signal at the third component terminal to a switch inorder to affect an output signal of the power conversion system. Thesystem controller is configured to, if the output load remains at afirst load magnitude, keep the first signal at a first signal magnitude.Furthermore, the system controller is configured to, if the output loadchanges from the first load magnitude to a second load magnitude, changethe first signal from the first signal magnitude to a second signalmagnitude during a first time period and change the first signal fromthe second signal magnitude to a third signal magnitude during a secondtime period following the first time period. The system controller isfurther configured to, if the output load remains at the second loadmagnitude, keep the first signal at the second signal magnitude. Thesecond time period is longer than the first time period. The thirdsignal magnitude is different from the first signal magnitude.

In one embodiment, a method for regulating a power conversion systemincludes receiving a reference signal and a feedback signal associatedwith an output signal of the power conversion system, generating a firstsignal based on at least information associated with the feedback signaland the reference signal, processing information associated with thefirst signal, and outputting a drive signal based on at leastinformation associated with the first signal to a switch in order toaffect the output signal of the power conversion system. The process forgenerating a first signal based on at least information associated withthe feedback signal and the reference signal includes, if an on-off modeis selected, setting a variable resistance value to a first resistancemagnitude, and if an error amplifier mode is selected, setting thevariable resistance value to a second resistance magnitude, the secondresistance magnitude being smaller than the first resistance magnitude,the on-off mode being different from the error amplifier mode.

In another embodiment, a method for regulating a power conversion systemincludes receiving a reference signal and a feedback signal associatedwith an output signal of the power conversion system and processinginformation associated with the feedback signal and the referencesignal. The method further includes generating a first signal based onat least information associated with the feedback signal and thereference signal, processing information associated with the firstsignal, and outputting a drive signal based on at least informationassociated with the first signal to a switch in order to affect theoutput signal of the power conversion system. The process for generatinga first signal based on at least information associated with thefeedback signal and the reference signal includes, if the powerconversion system operates in a first mode, in response to the feedbacksignal changing from a first signal magnitude to a second signalmagnitude, changing the first signal from a third signal magnitude to afourth signal magnitude during a first time period, and if the powerconversion system operates in a second mode, in response to the feedbacksignal changing from the first signal magnitude to the second signalmagnitude, changing the first signal from the third signal magnitude tothe fourth signal magnitude during a second time period, the second timeperiod being longer than the first time period in duration.

In yet another embodiment, a method for regulating a power conversionsystem includes receiving, by at least a first amplifier, a referencesignal and a feedback signal associated with an output load of the powerconversion system, the first amplifier including an amplifier terminalcoupled to a first component terminal of a variable-resistancecomponent, the variable-resistance component further including a secondcomponent terminal coupled to a first capacitor. In addition, the methodincludes processing information associated with the reference signal andthe feedback signal, generating, by at least the first amplifier and thevariable-resistance component, a first signal based on at leastinformation associated with the feedback signal and the referencesignal, and receiving the first signal by at least a modulation anddrive component, the modulation and drive component including a thirdcomponent terminal and a fourth component terminal coupled to theamplifier terminal. Further, the method includes processing informationassociated with the first signal, and outputting a drive signal to aswitch in order to affect an output signal of the power conversionsystem. The process for generating, by at least the first amplifier andthe variable-resistance component, a first signal includes, if theoutput load remains at a first load magnitude, keeping the first signalat a first signal magnitude. In addition, the process for generating, byat least the first amplifier and the variable-resistance component, afirst signal includes, if the output load changes from the first loadmagnitude to a second load magnitude, changing the first signal from thefirst signal magnitude to a second signal magnitude during a first timeperiod and changing the first signal from the second signal magnitude toa third signal magnitude during a second time period following the firsttime period. The process for generating, by at least the first amplifierand the variable-resistance component, a first signal further includes,if the output load remains at the second load magnitude, keeping thefirst signal at the second signal magnitude. The second time period islonger than the first time period. The third signal magnitude isdifferent from the first signal magnitude.

Many benefits are achieved by way of the present invention overconventional techniques. For example, some embodiments of the presentinvention implement a control scheme to improve dynamic response andmaintain system stability with a simple compensation network and a smallnumber of external components.

Depending upon embodiment, one or more benefits may be achieved. Thesebenefits and various additional objects, features and advantages of thepresent invention can be fully appreciated with reference to thedetailed description and accompanying drawings that follow.

4. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram showing a conventional switching powerconversion system with a step-down structure.

FIG. 2 is a simplified conventional diagram showing certain componentsof the system controller as part of the power conversion system as shownin FIG. 1.

FIG. 3 is a simplified diagram showing a power conversion systemaccording to one embodiment of the present invention.

FIG. 4(A) is a simplified diagram showing certain components of thesystem controller as part of the power conversion system as shown inFIG. 3 according to one embodiment of the present invention.

FIG. 4(B) is a simplified timing diagram for the system controller aspart of the power conversion system as shown in FIG. 3 according to oneembodiment of the present invention.

FIG. 5 is a simplified diagram showing certain components of the systemcontroller as part of the power conversion system operating in theon-off mode according to another embodiment of the present invention.

FIG. 6 is a simplified diagram showing certain components of the systemcontroller as part of the power conversion system in the transition modeaccording to another embodiment of the present invention.

FIG. 7 is a simplified diagram showing certain components of the systemcontroller as part of the power conversion system as shown in FIG. 3after the start-up process is completed according to yet anotherembodiment of the present invention.

FIG. 8(A) is a simplified timing diagram showing the signal generated bythe error amplifier and the voltage generated by the compensationcapacitor as parts of the power conversion system as shown in FIG. 3 ifthe output load changes from no/light load to full/heavy load accordingto one embodiment of the present invention.

FIG. 8(B) is a simplified diagram showing certain components of thesystem controller as part of the power conversion system if the outputload changes from no/light load to full/heavy load according to anotherembodiment of the present invention.

FIG. 9 is a simplified timing diagram showing the signal generated bythe error amplifier and the voltage generated by the compensationcapacitor as parts of the power conversion system if the output loadchanges from full/heavy load to no/light load according to anotherembodiment of the present invention.

5. DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to integrated circuits. Moreparticularly, the invention provides systems and methods for enhancingdynamic responses. Merely by way of example, the invention has beenapplied to power conversion systems. But it would be recognized that theinvention has a much broader range of applicability.

FIG. 3 is a simplified diagram showing a power conversion systemaccording to one embodiment of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. The switching powerconversion system 300 includes a system controller 302, a switch 334, acapacitor 336, two diodes 338 and 340, and an inductor 342. The systemcontroller 302 includes an error amplifier 308, a modulation component304, a gate driver 306, and a compensation network 326. The compensationnetwork 326 includes capacitors 310 and 312 and a variable-resistancecomponent 314. For example, the error amplifier 308, the modulationcomponent 304, the gate driver 306, the capacitor 310 and the component314 are on a same chip, while the capacitor 312 is on a different chip.In another example, the capacitor 312 is on a same chip as the erroramplifier 308, the modulation component 304, the gate driver 306, thecapacitor 310 and the component 314. In yet another example, themodulation component 304 can perform pulse-width-modulation (PWM)control, and/or pulse-frequency-modulation (PFM) control. In yet anotherexample, the variable-resistance component 314 is a variable resistor.

According to one embodiment, the error amplifier 308 receives a feedbacksignal 316 that is related to an output voltage 350 and a referencesignal 318 and generates a signal 320 which indicates load conditions ofthe system 300. For example, the modulation component 304 receives thesignal 320 and outputs a modulation signal 322 to the gate driver 306which generates a gate drive signal 324 to drive the switch 334. Inanother example, the compensation network 326 is connected to an outputterminal of the error amplifier 308.

According to another embodiment, the power conversion system 300operates in an error amplifier mode (EA mode) or an on-off mode. Forexample, if the resistance of the component 314 has a very largemagnitude (e.g., nearly infinity), the compensation capacitor 312 whichhas a large capacitance is disconnected from the output terminal of theerror amplifier 308. Then, the capacitor 310 which has a smallcapacitance becomes the only load connected to the error amplifier 308,and thus the system 300 operates in the on-off mode in some embodiments.For example, if the resistance of the component 314 becomes very small(e.g., nearly zero), the compensation capacitor 312 is connected to theerror amplifier 308, and the system 300 operates in the EA mode. Inanother example, if the resistance of the component 314 changes betweena very large magnitude (e.g., nearly infinity) and a very smallmagnitude (e.g., nearly zero), the system 300 operates in a transitionmode between the EA mode and the on-off mode. In yet another example, ifthe feedback signal 316 changes in magnitude, in response the signal 320changes in magnitude much faster in the on-off mode than in the EA mode.In yet another example, if the feedback signal 316 changes from amagnitude larger than the reference signal 318 to a magnitude smallerthan the reference signal 318, the signal 320 increases in magnitudemuch faster in the on-off mode than in the EA mode. In yet anotherexample, if the feedback signal 316 changes from a magnitude smallerthan the reference signal 318 to a magnitude larger than the referencesignal 318, the signal 320 decreases in magnitude much faster in theon-off mode than in the EA mode.

FIG. 4(A) is a simplified diagram showing certain components of thesystem controller 302 as part of the power conversion system 300according to one embodiment of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. The system controller 302further includes a logic control component 401. The component 314includes an amplifier 402, a variable resistor 404, a resistor 406, andswitches 408, 410, 412 and 414.

According to one embodiment, the logic control component 401 generatesthree control signals 416, 418 and 420. For example, the switch 408 isclosed or open in response to the control signal 416, and the switch 414is closed or open in response to a signal 417 which is complementary tothe control signal 416. In another example, the switch 412 is closed oropen in response to the signal 418, and the switch 410 is closed or openin response to the signal 420. In yet another example, a voltage bufferincluding the amplifier 402 and the switch 414 receives the signalamplified 320 generated by the error amplifier 308 and outputs a voltagesignal 422 to the compensation capacitor 312 if the switch 414 is closed(e.g., on). In yet another example, the capacitor 310 has a smallcapacitance, and the compensation capacitor 312 has a large capacitance.

FIG. 4(B) is a simplified timing diagram for the system controller 302as part of the power conversion system 300 according to one embodimentof the present invention. This diagram is merely an example, whichshould not unduly limit the scope of the claims. One of ordinary skillin the art would recognize many variations, alternatives, andmodifications. The waveform 480 represents the control signal 416 as afunction of time, the waveform 482 represents the control signal 418 asa function of time, and the waveform 484 represents the control signal420 as a function of time. The waveform 486 represents the signal 320 asa function of time, the waveform 488 represents the voltage signal 422as a function of time, and the waveform 492 represents the resistance ofthe resistor 404 as a function of time.

Six time periods, T₁, T₂, T₃, T₄, T₅ and T₆ are shown in FIG. 4(B). Forexample, the time period T₁ starts at time t₀ and ends at time t₁, thetime period T₂ starts at the time t₁ and ends at time t₂, and the timeperiod T₃ starts at the time t₂ and ends at time t₃. In another example,the time period T₄ starts at the time t₃ and ends at time t₅, the timeperiod T₅ starts at the time t₅ and ends at time t₆, and the time periodT₆ starts at the time t₆ and ends at time t₈. In yet another example,t₀≦t₁≦t₂≦t₃≦t₄≦t₅≦t₆≦t₇≦t₈.

According to one embodiment, during the time period T₁, the controlsignals 416, 418 and 420 are all at a logic low level, as shown by thewaveforms 480, 482 and 484 respectively. For example, in response, theswitches 408, 412 and 410 are open (e.g., off) respectively. In anotherexample, the resistor 404 does not affect the operation of thecontroller 302. In yet another example, the resistor 404 has a verylarge magnitude 494 (e.g., nearly infinity) as shown by the waveform492. The system 300 operates in the on-off mode according to certainembodiments. For example, the signal 417 that is complementary to thesignal 416 is at a logic high level, and in response the switch 414 isclosed (e.g., on). In yet another example, the amplifier 402 outputs thevoltage signal 422 through the closed switch 414, and the compensationcapacitor 312 is charged in response.

FIG. 5 is a simplified diagram showing certain components of the systemcontroller 302 as part of the power conversion system 300 operating inthe on-off mode according to another embodiment of the presentinvention. This diagram is merely an example, which should not undulylimit the scope of the claims. One of ordinary skill in the art wouldrecognize many variations, alternatives, and modifications. The switches408, 410, 412 and 414, and the resistors 404 and 406 are omitted in thisembodiment.

As shown in FIG. 4(A) and FIG. 5, a bandwidth of the buffering isdetermined, for example, as follows.

$\begin{matrix}{{BW} = \frac{G_{m\_ {op}1}}{C_{2}}} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$

where G_(m) _(_) _(op1) represents a transconductance of the amplifier402, and C₂ represents the capacitance of the capacitor 310.

If the power conversion system 300 operates in the on-off mode (e.g.,during T₁), the output voltage 350 reaches a stable level withoutovershoot over a wide range of input AC voltages and load conditionsaccording to certain embodiments. For example, after the output voltage350 reaches the stable level, the power conversion system 300 entersinto a transition mode between the on-off mode and the EA mode (e.g.,T₂) as shown in FIG. 4(B). In another example, the charges stored on thecompensation capacitor 312 smoothes out the transition if the powerconversion system 302 enters the time period T₂.

According to another embodiment, during the time period T₂, the controlsignal 418 changes to a logic high level, while the control signal 416and 420 remains at the logic low level (e.g., as shown by the waveforms480, 482 and 484). For example, in response, the switch 412 is closed(e.g., on), and both the resistor 404 and the resistor 406 are connectedbetween the error amplifier 308 and the compensation capacitor 312. Inanother example, during the time period T₂, the resistance of theresistor 404 decreases (e.g., linearly or non-linearly) from the verylarge magnitude 494 (e.g., nearly infinity at t₁) to a very smallmagnitude 496 (e.g., nearly zero at t₂). In yet another example, thechange of resistance of the resistor 404 is controlled by the logiccontrol component 401.

FIG. 6 is a simplified diagram showing certain components of the systemcontroller 302 as part of the power conversion system 300 in thetransition mode according to another embodiment of the presentinvention. This diagram is merely an example, which should not undulylimit the scope of the claims. One of ordinary skill in the art wouldrecognize many variations, alternatives, and modifications. The switches408, 410, 412 and 414 are omitted in this embodiment.

Referring back to FIG. 4(A) and FIG. 4(B), at the end of the time periodT₂ (e.g., at t₂), the control signal 420 changes from the logic lowlevel to the logic high level in some embodiments. For example, inresponse the switch 410 is closed (e.g., on) and the resistor 404 isshorted. As the power conversion system 300 enters into the time periodT₃ (e.g., at t₂), the start-up process is completed and the powerconversion system 300 begins normal operations according to certainembodiments. For example, during the time period T₄, the time period T₅,and/or the time period T₆, the power conversion system 300 operates inthe EA mode.

FIG. 7 is a simplified diagram showing certain components of the systemcontroller 302 as part of the power conversion system 300 after thestart-up process is completed according to yet another embodiment of thepresent invention. This diagram is merely an example, which should notunduly limit the scope of the claims. One of ordinary skill in the artwould recognize many variations, alternatives, and modifications. Theswitches 408, 410, 412 and 414 and the resistor 404 are omitted in thisembodiment.

If the power conversion system 300 changes between no/light output loadconditions and full/heavy output load conditions, the system controller302 adjusts accordingly to provide a satisfactory dynamic response insome embodiments. Referring back to FIG. 4(B), for example, if the powerconversion system 300 changes from no/light load conditions tofull/heavy load conditions at the beginning of the time period T₄ (e.g.,at t₃), in response, the output voltage 350 decreases in magnitude, andthe feedback signal 316 also decreases in magnitude. Since the capacitor310 has a small capacitance and the compensation capacitor 312 isconnected to the output terminal of the error amplifier 308, the signal320 (e.g., V_(comp) _(_) _(in)) increases in magnitude (e.g., as shownby the waveform 486), as an example. In another example, the signal 320becomes larger in magnitude than the voltage signal 422 (e.g., V_(comp))which indicates the change of the output load conditions. In yet anotherexample, the modulation component 304 increases the switching frequencyand/or duty cycles of the system 300 to deliver more power to theoutput. In yet another example, during the time period T₄, the signal320 (e.g., V_(comp) _(_) _(in)) increases to a maximum magnitude 810(e.g., at t₄) and then decreases to become approximately equal inmagnitude to the voltage signal 422 (e.g., V_(comp)) at the end of thetime period T₄ (e.g., t₅) as shown by the waveforms 486 and 490. Incertain embodiments, during the time period T₄, the power conversionsystem 300 operates in a pseudo-on-off mode which enhances the dynamicresponse of the system 300. The comparison of the signal 320 and thevoltage signal 422 shown in FIG. 8(A) illustrates that the powerconversion system 300 operates in such a pseudo-on-off mode.

FIG. 8(A) is a simplified timing diagram showing the signal 320generated by the error amplifier 308 and the voltage 422 generated bythe compensation capacitor 312 as parts of the power conversion system300 if the output load changes from no/light load to full/heavy loadaccording to one embodiment of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. The waveform 802 representsthe signal 320 as a function of time, and the waveform 804 representsthe voltage 422 as a function of time.

In one embodiment, before t₃, the signal 320 and the voltage 422 haveapproximately a same magnitude 806 (e.g., as shown by the waveforms 802and 804). For example, after t₃, the signal 320 increases in magnitudemuch faster than the voltage 422. In another example, the signal 320reaches the maximum magnitude 810 (e.g., at t₄) and then begins todecreases in magnitude (e.g., as shown by the waveform 802). In yetanother example, at the end of the time period T₄, the signal 320 andthe voltage 422 have approximately a same magnitude 808 (e.g., at t₅ asshown by the waveforms 802 and 804). In yet another example, the timeperiod between t₃ and t₄ is much shorter than the time period between t₄and t₅.

If the signal 320 increases to the maximum magnitude 810 too quicklyand/or the maximum magnitude 810 is too high, the power conversionsystem 300 essentially enters the on-off mode which may results inoutput instability and/or audible noise according to certainembodiments. For example, in order to keep the power conversion system300 from entering the on-off mode, the logic control component 401changes the control signal 416 to the logic high level (e.g., themagnitude 498 as shown in FIG. 4(B)) to close the switch 408. In anotherexample, the resistor 406 is thus shorted, and the compensationcapacitor 312 is connected directly to the output terminal of the erroramplifier 308 as shown in FIG. 8(B).

FIG. 8(B) is a simplified diagram showing certain components of thesystem controller 302 as part of the power conversion system 300 if theoutput load changes from no/light load to full/heavy load according toanother embodiment of the present invention. This diagram is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. The switches 408, 410, 412 and 414, the resistors 404and 406, and the amplifier 402 are omitted in this embodiment.

Referring back to FIG. 4(B), after the signal 320 (e.g., V_(comp) _(_)_(in)) and the voltage signal 422 (e.g., V_(comp)) become approximatelyequal in magnitude at the end of the time period T₄ (e.g., t₅), thepower conversion system 300 returns to the normal operations in theerror amplifier mode and the signal 320 (e.g., V_(comp) _(_) _(in)) andthe voltage signal 422 (e.g., V_(comp)) remain approximately unchangedin magnitude during the time period T₅ (e.g., as shown by the waveforms486 and 490).

In one embodiment, if the power conversion system 300 changes fromfull/heavy load conditions to no/light load conditions at the beginningof the time period T₆ (e.g., at t₆), in response, the output voltage 350increases in magnitude, and the feedback signal 316 also increases inmagnitude. Since the capacitor 310 has a small capacitance and thecompensation capacitor 312 is connected to the output terminal of theerror amplifier 308, the signal 320 (e.g., V_(comp) _(_) _(in))decreases in magnitude (e.g., at t₆ as shown by the waveform 486), as anexample. In another example, the signal 320 becomes lower in magnitudethan the voltage signal 422 (e.g., V_(comp)) which indicates the changeof the output load conditions. In yet another example, the modulationcomponent 304 decreases the switching frequency and/or duty cycles ofthe system 300 to deliver less power to the output. In yet anotherexample, during the time period T₆, the signal 320 (e.g., V_(comp) _(_)_(in)) decreases to a minimum magnitude 908 (e.g., at t₇) and thenincreases to become approximately equal in magnitude to the voltagesignal 422 (e.g., V_(comp)) at the end of the time period T₆ (e.g., att₈ as shown by the waveforms 486 and 490). In certain embodiments,during the time period T₆, the power conversion system 300 operates in apseudo-on-off mode which enhances the dynamic response of the system300. The comparison of the signal 320 and the voltage signal 422 shownin FIG. 9 illustrates that the power conversion system 300 operates insuch a pseudo-on-off mode.

FIG. 9 is a simplified timing diagram showing the signal 320 generatedby the error amplifier 308 and the voltage 422 generated by thecompensation capacitor 312 as parts of the power conversion system 300if the output load changes from full/heavy load to no/light loadaccording to another embodiment of the present invention. This diagramis merely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. The waveform 902 representsthe signal 320 as a function of time, and the waveform 904 representsthe voltage 422 as a function of time.

In one embodiment, before t₆, the signal 320 and the voltage 422 haveapproximately a same magnitude 906 (e.g., as shown by the waveforms 902and 904). For example, after t₆, the signal 320 decreases in magnitudemuch faster than the voltage 422. In another example, the signal 320reaches the minimum magnitude 908 (e.g., at t₇) and then begins toincreases in magnitude (e.g., as shown by the waveform 902). In yetanother example, at the end of the time period T₆, the signal 320 andthe voltage 422 have approximately a same magnitude 910 (e.g., at t₈ asshown by the waveforms 902 and 904). In yet another example, the timeperiod between t₆ and t₇ is much shorter than the time period between t₇and t₈. In yet another example, after the time period T₆, the signal 320and the voltage 422 keep at the magnitude 910, and the system 300performs normal operations in the error amplifier mode.

As discussed above and further emphasized here, FIGS. 4(A), 4(B), 8(A)and 9 are merely examples, which should not unduly limit the scope ofthe claims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. For example, the logiccontrol component 401 detects when the start-up process of the powerconversion system 300 begins, and determines whether the systemcontroller 302 should operate in the on-off mode, in the transition modebetween the on-off mode to the error amplifier mode, or in the erroramplifier mode. In one embodiment, the system controller 302 operates inthe on-off mode, then in the transition mode between the on-off mode tothe error amplifier mode, and then in the error amplifier mode,sequentially in time since the beginning of the start-up process. Inanother embodiment, the system controller 302 operates in the on-offmode for the time period T₁, then in the transition mode between theon-off mode to the error amplifier mode for the time period T₂, and thenin the error amplifier mode for the time period T₃. In yet anotherembodiment, the durations of the time period T₁, the time period T₂and/or the time period T₃ are determined by the logic control component401 through the signals 416, 418 and/or 420.

In another example, the logic control component 401 detects changes inload condition (e.g., through the signal 422 and/or the signal 320), anddetermines whether the signals 416, 418 and/or 420 should be changed(e.g., during the time period T₄, the time period T₅, and/or the timeperiod T₆). In one embodiment, the time period T₆ precedes the timeperiod T₄. In another embodiment, if the output load of the powerconversion system 300 does not change from no/light load to full/heavyload, the time period T₄ is omitted from FIG. 4(B). In yet anotherembodiment, if the output load of the power conversion system 300 doesnot change from full/heavy load to no/light load, the time period T₆ isomitted. In yet another embodiment, if the output load of the powerconversion system 300 does not change from no/light load to full/heavyload and does not change from full/heavy load to no/light load, both thetime period T₄ and the time period T₆ are omitted; hence the time periodT₃ continues and the power conversion system 300 performs normaloperations under the error amplifier mode.

According to another embodiment, a system controller for regulating apower conversion system includes a first amplifier (e.g., the amplifier308), a variable-resistance component (e.g., the component 314), a firstcapacitor (e.g., the capacitor 312), and a modulation and drivecomponent (e.g., the modulation component 304 and the gate driver 306).The first amplifier is configured to receive a reference signal and afeedback signal associated with an output signal of the power conversionsystem, the first amplifier including an amplifier terminal. Thevariable-resistance component is associated with a first variableresistance value, the variable-resistance component including a firstcomponent terminal and a second component terminal, the first componentterminal being coupled with the amplifier terminal. The first capacitorincludes a first capacitor terminal and a second capacitor terminal, thefirst capacitor terminal being coupled with the second componentterminal. The modulation and drive component includes a first terminaland a second terminal, the first terminal being coupled with theamplifier terminal, the modulation and drive component being configuredto output a drive signal at the second terminal to a switch in order toaffect the output signal of the power conversion system. The systemcontroller is configured to set the first variable resistance value to afirst resistance magnitude in order to operate in an on-off mode, andset the first variable resistance value to a second resistance magnitudein order to operate in an error amplifier mode. The first resistancemagnitude is larger than the second resistance magnitude. The on-offmode is different from the error amplifier mode. For example, the systemcontroller is implemented according to FIG. 3, FIG. 4(A), FIG. 4(B),FIG. 5, FIG. 6, FIG. 7, FIG. 8(A), FIG. 8(B), and/or FIG. 9.

In one embodiment, the first amplifier is configured to generate, withat least the variable-resistance component, a first signal based on atleast information associated with the feedback signal and the referencesignal. For example, the modulation and drive component is configured toreceive the first signal and generate the drive signal based on at leastinformation associated with the first signal. In another example, thesystem controller includes a second capacitor including a thirdcapacitor terminal and a fourth capacitor terminal, the third capacitorterminal being coupled to the amplifier terminal. In yet anotherexample, the system controller is further configured to detect a secondsignal associated with the first capacitor terminal, if the first signalis larger than the second signal in magnitude, change the drive signalin order to increase the output signal in magnitude, and if the firstsignal is smaller than the second signal in magnitude, change the drivesignal in order to decrease the output signal in magnitude.

In another embodiment, the system controller is further configured to,in the on-off mode, if the feedback signal changes from a first signalmagnitude to a second signal magnitude, change the first signal from athird signal magnitude to a fourth signal magnitude during a first timeperiod. For example, the system controller is further configured to, inthe error amplifier mode, if the feedback signal changes from the firstsignal magnitude to the second signal magnitude, change the first signalfrom the third signal magnitude to the fourth signal magnitude during asecond time period. In another example, the second time period is longerthan the first time period in duration. In yet another example, thefirst signal magnitude is smaller than the reference signal, and thesecond signal magnitude is larger than the reference signal. In yetanother example, the first signal magnitude is larger than the referencesignal, and the second signal magnitude is smaller than the referencesignal.

In yet another embodiment, the system controller is further configuredto, during a first time period, set the first variable resistance valueto the first resistance magnitude in order to operate in the on-offmode, during a second time period, change the first variable resistancevalue from the first resistance magnitude to the second resistancemagnitude, and during a third time period, set the first variableresistance value to the second resistance magnitude in order to operatein the error amplifier mode. For example, the modulation and drivecomponent includes a modulation component and a gate drive component. Inanother example, the modulation component is configured to generate amodulation signal based on at least information associated with thefirst signal. In yet another example, the gate drive component isconfigured to receive the modulation signal and generate the drivesignal based on at least information associated with the modulationsignal. In yet another example, the first capacitor terminal is coupleddirectly with the second component terminal.

In yet another embodiment, the system controller further includes asecond capacitor including a third capacitor terminal and a fourthcapacitor terminal, the third capacitor terminal being coupled to theamplifier terminal. For example, the variable-resistance componentincludes a second amplifier configured to receive a first signalgenerated by at least the second capacitor and output a second signalbased on at least information associated with the first signal, thesecond signal being equal in magnitude to an average of the first signalover a time period. In another example, during the time period, thesystem controller operates in the on-off mode. In yet another example,during the time period, the system controller operates in the erroramplifier mode. In yet another example, during the time period, thesystem controller operates to change from the on-off mode to the erroramplifier mode.

According to another embodiment, a system controller for regulating apower conversion system includes a first amplifier (e.g., the amplifier308), a second amplifier (e.g., the amplifier 402), a first capacitor(e.g., the capacitor 312), a first switch (e.g., the switch 408), asecond switch (e.g., the switch 412), a third switch (e.g., the switch410), a fourth switch (e.g., the switch 414), a first resistor (e.g.,the resistor 406), and a second resistor (e.g., the resistor 404). Thefirst amplifier includes a first input terminal and a second inputterminal and a first output terminal. The second amplifier includes athird input terminal and a fourth input terminal and a second outputterminal. The first capacitor includes a first capacitor terminal and asecond capacitor terminal. The first switch includes a first switchterminal and a second switch terminal. The second switch includes athird switch terminal and a fourth switch terminal. The third switchincludes a fifth switch terminal and a sixth switch terminal. The fourthswitch includes a seventh switch terminal and an eighth switch terminal.The first resistor includes a first resistor terminal and a secondresistor terminal. The second resistor includes a third resistorterminal and a fourth resistor terminal, the second resistor beingassociated with a variable resistance value. The seventh switch terminalis coupled to the second output terminal. The eighth switch terminal iscoupled to the fourth input terminal, the first capacitor terminal, thesecond switch terminal, and the first capacitor terminal. The thirdswitch terminal is coupled to the fifth switch terminal. The fourthswitch terminal is coupled to the third resistor terminal. The fourthresistor terminal is coupled to the sixth switch terminal, the firstresistor terminal, and the first switch terminal. For example, thesystem controller is implemented according to at least FIG. 3 and/orFIG. 4(A).

In one embodiment, the first amplifier is further configured to receiveat the first input terminal a feedback signal associated with an outputsignal of the power conversion system and a reference signal at thesecond input terminal and generate at the first output terminal a firstsignal based on at least information associated with the feedback signaland the reference signal. For example, the system controller furtherincludes a modulation and drive component including a first terminal anda second terminal, the first terminal being coupled with the firstoutput terminal, the modulation and drive component being configured tooutput a drive signal at the second terminal to a switch in order toaffect the output signal of the power conversion system. In anotherexample, the system controller further includes a second capacitorincluding a third capacitor terminal and a fourth capacitor terminal,the third capacitor terminal being coupled to the first output terminal.In yet another example, the system controller is further configured todetect a second signal associated with the first capacitor terminal, ifthe first signal is larger than the second signal in magnitude, changethe drive signal in order to increase the output signal in magnitude,and if the first signal is smaller than the second signal in magnitude,change the drive signal in order to decrease the output signal inmagnitude.

In another embodiment, the system controller further includes a logiccontrol component configured to generate a first control signal, asecond control signal and a third control signal. For example, during afirst time period, the first switch is configured to be open in responseto the first control signal, the second switch is configured to be openin response to the second control signal, the third switch is configuredto be open in response to the third control signal, and the fourthswitch is configured to be closed in response to the first controlsignal. In another example, during a second time period, the firstswitch is configured to be open in response to the first control signal,the second switch is configured to be closed in response to the secondcontrol signal, the third switch is configured to be open in response tothe third control signal, and the fourth switch is configured to beclosed in response to the first control signal. In yet another example,during a third time period, the first switch is configured to be open inresponse to the first control signal, the second switch is configured tobe closed in response to the second control signal, the third switch isconfigured to be closed in response to the third control signal, and thefourth switch is configured to be closed in response to the firstcontrol signal.

According to yet another embodiment, a system controller for regulatinga power conversion system includes a variable-resistance component(e.g., the component 314), a first amplifier (e.g., the amplifier 308),a first capacitor (e.g., the capacitor 312) and a modulation and drivecomponent (e.g., the modulation component 304 and the gate driver 306).The variable-resistance component includes a first component terminaland a second component terminal and is associated with a first variableresistance value. The first amplifier is configured to receive areference signal and a feedback signal associated with an output signalof the power conversion system, the first amplifier including anamplifier terminal coupled with the first component terminal, the firstamplifier being further configured to generate, with at least thevariable-resistance component, a first signal based on at leastinformation associated with the feedback signal and the referencesignal. The first capacitor includes a first capacitor terminal and asecond capacitor terminal, the first capacitor terminal being coupledwith the second component terminal. The modulation and drive componentincludes a first terminal and a second terminal, the first terminalbeing coupled with the amplifier terminal, the modulation and drivecomponent being configured to output a drive signal at the secondterminal to a switch in order to affect the output signal of the powerconversion system. The system controller is configured to set the firstvariable resistance value to a first resistance magnitude in order tooperate in a first mode, and set the first variable resistance value toa second resistance magnitude in order to operate in a second mode. Thesystem controller is further configured to, in the first mode, if thefeedback signal changes from a first signal magnitude to a second signalmagnitude, change the first signal from a third signal magnitude to afourth signal magnitude during a first time period. The systemcontroller is further configured to, in the second mode, if the feedbacksignal changes from the first signal magnitude to the second signalmagnitude, change the first signal from the third signal magnitude tothe fourth signal magnitude during a second time period, the second timeperiod being longer than the first time period in duration. For example,the system controller is implemented according to FIG. 3, FIG. 4(A),FIG. 4(B), FIG. 5, FIG. 6, FIG. 7, FIG. 8(A), FIG. 8(B), and/or FIG. 9.

In one embodiment, the second resistance magnitude is smaller than thefirst resistance magnitude. For example, the first signal magnitude issmaller than the reference signal, and the second signal magnitude islarger than the reference signal. In another example, the first signalmagnitude is larger than the reference signal, and the second signalmagnitude is smaller than the reference signal.

In another embodiment, the system controller further includes a secondcapacitor including a third capacitor terminal and a fourth capacitorterminal, the third capacitor terminal being coupled to the amplifierterminal. For example, the variable-resistance component includes asecond amplifier configured to receive a first signal generated by atleast the second capacitor and output a second signal based on at leastinformation associated with the first signal, the second signal beingequal in magnitude to an average of the first signal over a time period.In another example, during the time period, the system controlleroperates in the on-off mode. In yet another example, during the timeperiod, the system controller operates in the error amplifier mode. Inyet another example, during the time period, the system controlleroperates to change from the on-off mode to the error amplifier mode.

In yet another embodiment, a system controller for regulating a powerconversion system includes a variable-resistance component, a firstamplifier, a first capacitor and a modulation and drive component. Thevariable-resistance component includes a first component terminal and asecond component terminal and is associated with a first variableresistance value. The first amplifier is configured to receive areference signal and a feedback signal associated with an output load ofthe power conversion system, the first amplifier including an amplifierterminal coupled with the first component terminal, the first amplifierbeing further configured to generate, with at least thevariable-resistance component, a first signal based on at leastinformation associated with the feedback signal and the referencesignal. The first capacitor includes a first capacitor terminal and asecond capacitor terminal, the first capacitor terminal being coupledwith the second component terminal. In addition, the modulation anddrive component includes a third component terminal and a fourthcomponent terminal, the fourth component terminal being coupled with theamplifier terminal, the modulation and drive component being configuredto output a drive signal at the third component terminal to a switch inorder to affect an output signal of the power conversion system. Thesystem controller is configured to, if the output load remains at afirst load magnitude, keep the first signal at a first signal magnitude.Furthermore, the system controller is configured to, if the output loadchanges from the first load magnitude to a second load magnitude, changethe first signal from the first signal magnitude to a second signalmagnitude during a first time period and change the first signal fromthe second signal magnitude to a third signal magnitude during a secondtime period following the first time period. The system controller isfurther configured to, if the output load remains at the second loadmagnitude, keep the first signal at the second signal magnitude. Thesecond time period is longer than the first time period. The thirdsignal magnitude is different from the first signal magnitude. Forexample, the system controller is implemented according to FIG. 3, FIG.4(A), FIG. 4(B), FIG. 7, FIG. 8(A), FIG. 8(B), and/or FIG. 9.

According to another embodiment, a method for regulating a powerconversion system includes receiving a reference signal and a feedbacksignal associated with an output signal of the power conversion system,generating a first signal based on at least information associated withthe feedback signal and the reference signal, processing informationassociated with the first signal, and outputting a drive signal based onat least information associated with the first signal to a switch inorder to affect the output signal of the power conversion system. Theprocess for generating a first signal based on at least informationassociated with the feedback signal and the reference signal includes,if an on-off mode is selected, setting a variable resistance value to afirst resistance magnitude, and if an error amplifier mode is selected,setting the variable resistance value to a second resistance magnitude,the second resistance magnitude being smaller than the first resistancemagnitude, the on-off mode being different from the error amplifiermode. For example, the method is implemented according to FIG. 3, FIG.4(A), FIG. 4(B), FIG. 5, FIG. 6, FIG. 7, FIG. 8(A), FIG. 8(B), and/orFIG. 9.

According to yet another embodiment, a method for regulating a powerconversion system includes receiving a reference signal and a feedbacksignal associated with an output signal of the power conversion systemand processing information associated with the feedback signal and thereference signal. The method further includes generating a first signalbased on at least information associated with the feedback signal andthe reference signal, processing information associated with the firstsignal, and outputting a drive signal based on at least informationassociated with the first signal to a switch in order to affect theoutput signal of the power conversion system. The process for generatinga first signal based on at least information associated with thefeedback signal and the reference signal includes, if the powerconversion system operates in a first mode, in response to the feedbacksignal changing from a first signal magnitude to a second signalmagnitude, changing the first signal from a third signal magnitude to afourth signal magnitude during a first time period, and if the powerconversion system operates in a second mode, in response to the feedbacksignal changing from the first signal magnitude to the second signalmagnitude, changing the first signal from the third signal magnitude tothe fourth signal magnitude during a second time period, the second timeperiod being longer than the first time period in duration. For example,the method is implemented according to FIG. 3, FIG. 4(A), FIG. 4(B),FIG. 5, FIG. 6, FIG. 7, FIG. 8(A), FIG. 8(B), and/or FIG. 9.

In one embodiment, a method for regulating a power conversion systemincludes receiving, by at least a first amplifier, a reference signaland a feedback signal associated with an output load of the powerconversion system, the first amplifier including an amplifier terminalcoupled to a first component terminal of a variable-resistancecomponent, the variable-resistance component further including a secondcomponent terminal coupled to a first capacitor. In addition, the methodincludes processing information associated with the reference signal andthe feedback signal, generating, by at least the first amplifier and thevariable-resistance component, a first signal based on at leastinformation associated with the feedback signal and the referencesignal, and receiving the first signal by at least a modulation anddrive component, the modulation and drive component including a thirdcomponent terminal and a fourth component terminal coupled to theamplifier terminal. Further, the method includes processing informationassociated with the first signal, and outputting a drive signal to aswitch in order to affect an output signal of the power conversionsystem. The process for generating, by at least the first amplifier andthe variable-resistance component, a first signal includes, if theoutput load remains at a first load magnitude, keeping the first signalat a first signal magnitude. In addition, the process for generating, byat least the first amplifier and the variable-resistance component, afirst signal includes, if the output load changes from the first loadmagnitude to a second load magnitude, changing the first signal from thefirst signal magnitude to a second signal magnitude during a first timeperiod and changing the first signal from the second signal magnitude toa third signal magnitude during a second time period following the firsttime period. The process for generating, by at least the first amplifierand the variable-resistance component, a first signal further includes,if the output load remains at the second load magnitude, keeping thefirst signal at the second signal magnitude. The second time period islonger than the first time period. The third signal magnitude isdifferent from the first signal magnitude. For example, the method isimplemented according to FIG. 3, FIG. 4(A), FIG. 4(B), FIG. 7, FIG.8(A), FIG. 8(B), and/or FIG. 9.

For example, some or all components of various embodiments of thepresent invention each are, individually and/or in combination with atleast another component, implemented using one or more softwarecomponents, one or more hardware components, and/or one or morecombinations of software and hardware components. In another example,some or all components of various embodiments of the present inventioneach are, individually and/or in combination with at least anothercomponent, implemented in one or more circuits, such as one or moreanalog circuits and/or one or more digital circuits. In yet anotherexample, various embodiments and/or examples of the present inventioncan be combined.

Although specific embodiments of the present invention have beendescribed, it will be understood by those of skill in the art that thereare other embodiments that are equivalent to the described embodiments.Accordingly, it is to be understood that the invention is not to belimited by the specific illustrated embodiments, but only by the scopeof the appended claims.

1. A system controller for regulating a power conversion system, thesystem controller comprising: a first amplifier configured to receive areference signal and a feedback signal associated with an output signalof the power conversion system, the first amplifier including anamplifier terminal; a variable-resistance component associated with afirst variable resistance value, the variable-resistance componentincluding a first component terminal and a second component terminal,the first component terminal being coupled with the amplifier terminal;a first capacitor including a first capacitor terminal and a secondcapacitor terminal, the first capacitor terminal being coupled with thesecond component terminal; and a modulation and drive componentincluding a first terminal and a second terminal, the first terminalbeing coupled with the amplifier terminal, the modulation and drivecomponent being configured to output a drive signal at the secondterminal to a switch in order to affect the output signal of the powerconversion system; wherein the system controller is configured to: setthe first variable resistance value to a first resistance magnitude inorder to operate in an on-off mode; and set the first variableresistance value to a second resistance magnitude in order to operate inan error amplifier mode; wherein: the first resistance magnitude islarger than the second resistance magnitude; and the on-off mode isdifferent from the error amplifier mode.
 2. The system controller ofclaim 1 wherein: the first amplifier is configured to generate, with atleast the variable-resistance component, a first signal based on atleast information associated with the feedback signal and the referencesignal; and the modulation and drive component is configured to receivethe first signal and generate the drive signal based on at leastinformation associated with the first signal. 3.-17. (canceled)
 18. Thesystem controller of claim 1 wherein: the modulation and drive componentincludes a modulation component and a gate drive component; themodulation component is configured to generate a modulation signal basedon at least information associated with the first signal; and the gatedrive component is configured to receive the modulation signal andgenerate the drive signal based on at least information associated withthe modulation signal.
 19. The system controller of claim 1 wherein thefirst capacitor terminal is coupled directly with the second componentterminal. 20.-45. (canceled)
 46. A method for regulating a powerconversion system, the method comprising: receiving a reference signaland a feedback signal associated with an output signal of the powerconversion system; generating a first signal based on at leastinformation associated with the feedback signal and the referencesignal; processing information associated with the first signal;outputting a drive signal based on at least information associated withthe first signal to a switch in order to affect the output signal of thepower conversion system; wherein the process for generating a firstsignal based on at least information associated with the feedback signaland the reference signal includes: if an on-off mode is selected,setting a variable resistance value to a first resistance magnitude; andif an error amplifier mode is selected, setting the variable resistancevalue to a second resistance magnitude, the second resistance magnitudebeing smaller than the first resistance magnitude, the on-off mode beingdifferent from the error amplifier mode. 47.-48. (canceled)